What does it mean when "Lost Frames" occur on the EtherCAT bus?
There is little we can do. A "Lost Frame" is a HW problem, and it happens when the PHY has no link. We can only recommend cable and/or device replacement. See here:
https://www.ethercat.org/download/documents/EtherCAT_Diagnosis_For_Users_DE.pdf
Would it be possible to change the Device ID by an EtherCAT controller?
Yes, you can do this with by the Station Alias Configuration via the EtherCAT Master. You can find the documentation in the ETG 1020 chapter 18 - Explicit Device Identification:
The Device Identification value can be set
by an ID-Selector, locally on the slave This can be a Switch (e.g. Rotary- or DIP-switch) or set via a display control stored non-volatile. The ID-Selector should have a length of 16 Bit.
For example, Modbus Registers, etc.
By a configuration tool in the SII Configured Station Alias, The value of the SII is automatically loaded during boot-up of the ESC to the Configured Station Alias Register (0x0012).
By using the EtherCAT Controller